The present invention relates to a method of producing a magnetic disk, and more particularly to a method of producing a magnetic disk which method uses a lapping tape suitable for lapping the surface of a magnetic disk containing hard fillers (such as particles of Al.sub.2 O.sub.3, SiC, or the like).
With the recent increase in the recording density of a magnetic disk, it has become increasingly important to reduce, as much as possible, the distance between a magnetic head and the surface of a magnetic disk, namely the amount by which the head floats above the surface of the disk. For this reason, it is required to minimize the roughness of the surface of the magnetic disk. In order to lap the surface of magnetic disk medium so as to minimize the surface roughness, the surface is moved while the lapping tape is forced onto the surface.
In producing magnetic disks, the following are some examples of conventional methods known in the art employing lapping tape: the method disclosed in Japanese Unexamined Patent Publication No. 56-130834 in which the surface of lapping tape is previously coated with lubricant, the tape being used to lap after it has been dried at a temperature between 30 .degree. to 50.degree. C.; and the method disclosed in Japanese Unexamined Patent Publication No. 56-130836 in which a magnetic disk is prepared which has a magnetic film formed on a substrate and having a large surface-roughness occurring by a binder of thermosetting resin such as epoxy resin, phenolic resin, or melamine resin, and by fillers such as alumina powder, and the thus prepared magnetic disk is lapped while being moved relative to a magnetic head on which a lapping tape impregnated with a lubricant such as fluorocarbon is mounted.
The conventional lapping tape on which abrasive particles of Al.sub.2 O.sub.3, SiC or the like are provided is insufficient to adequately cut protrusions or heads occurring by fillers protruding from the surface of the magnetic medium when used in lapping the surface of the medium in which such fillers (particles of Al.sub.2 O.sub.3 having a particle size of 0.5 to 1.3 .mu.m) are contained as a durability-and-strength increasing agent, so that the conventional lapping tape is impossible to reduce the distance by which a magnetic head floats above the surface. On the other hand, with the type of a lapping tape incorporating abrasive particles of diamond which have an improved ability to cut the protrusions caused by fillers, the following problems has occurred. Namely, when the proportion of abrasive particles contained in a lapping tape is low, the resulting magnetic medium surface lapped by the lapping tape will have a lot of flaws caused as a result of the lapping working. Conversely, when the proportion of abrasive particles adopted is sufficient for the formation of chip pockets which can prevent the flaws from being caused, the expense would be too high for mass production of the magnetic disk.